package com.jdy.haoduoai.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64 {

  private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
      .toCharArray();

  /** Base64 encode the given data */
  public static String encode(byte[] data) {
    int start = 0;
    int len = data.length;
    StringBuffer buf = new StringBuffer(data.length * 3 / 2);

    int end = len - 3;
    int i = start;
    // int n = 0;

    while (i <= end) {
      int d = (((data[i]) & 0x0ff) << 16) | (((data[i + 1]) & 0x0ff) << 8)
          | ((data[i + 2]) & 0x0ff);

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append(legalChars[d & 63]);

      i += 3;

      /*
       * if (n++ >= 14) { n = 0; buf.append(" "); }
       */
    }

    if (i == start + len - 2) {
      int d = (((data[i]) & 0x0ff) << 16) | (((data[i + 1]) & 255) << 8);

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append(legalChars[(d >> 6) & 63]);
      buf.append("=");
    } else if (i == start + len - 1) {
      int d = ((data[i]) & 0x0ff) << 16;

      buf.append(legalChars[(d >> 18) & 63]);
      buf.append(legalChars[(d >> 12) & 63]);
      buf.append("==");
    }

    return buf.toString();
  }

  /**
   * Decodes the given Base64 encoded String to a new byte array. The byte array
   * holding the decoded data is returned.
   */

  public static byte[] decode(String s) {

    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    try {
      decode(s, bos);
    } catch (IOException e) {
      throw new RuntimeException();
    }
    byte[] decodedBytes = bos.toByteArray();
    try {
      bos.close();
      bos = null;
    } catch (IOException ex) {
      System.err.println("Error while decoding BASE64: " + ex.toString());
    }
    return decodedBytes;
  }

  private static int decode(char c) {
    if (c >= 'A' && c <= 'Z') {
      return (c) - 65;
    } else if (c >= 'a' && c <= 'z') {
      return (c) - 97 + 26;
    } else if (c >= '0' && c <= '9') {
      return (c) - 48 + 26 + 26;
    } else {
      switch (c) {
      case '+':
        return 62;
      case '/':
        return 63;
      case '=':
        return 0;
      default:
        throw new RuntimeException("unexpected code: " + c);
      }
    }
  }

  private static void decode(String s, OutputStream os) throws IOException {
    int i = 0;

    int len = s.length();

    while (true) {
      while (i < len && s.charAt(i) <= ' ') {
        i++;
      }

      if (i == len) {
        break;
      }

      int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12)
          + (decode(s.charAt(i + 2)) << 6) + (decode(s.charAt(i + 3)));

      os.write((tri >> 16) & 255);
      if (s.charAt(i + 2) == '=') {
        break;
      }
      os.write((tri >> 8) & 255);
      if (s.charAt(i + 3) == '=') {
        break;
      }
      os.write(tri & 255);

      i += 4;
    }
  }

}
